JP2007022277A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improving ice braking performance and ice turning performance by avoiding the groove width of sipe from becoming narrow when the load is applied. <P>SOLUTION: The pneumatic tire is equipped with a tread pattern having a land part 1 having the sipe 10 to be formed. The sipe 10 having the groove width of 0.2 to 0.6 mm is provided on the land part 1 with a sipe density of 0.1 to 0.2 mm/mm<SP>2</SP>, and a plurality of small holes 11 of not less than 3 mm depth are provided along the sipe 10 on the land part 1 divided by the sipe 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire including a tread pattern having a land portion in which sipes and small holes are formed, and is particularly useful as a studless tire (winter tire).

  Conventionally, in order to improve the ice performance of a studless tire, a tire pattern in which a plurality of sipes are arranged in each part (center part, mediate part, shoulder part) is known. As the shape of the sipe, a sipe having a straight or corrugated cross section is generally used. By forming such sipes in blocks, the edge effect, the water removal effect, and the adhesion effect are improved, and therefore the number of sipes tends to increase in recent years.

However, when a load is applied to the block provided with the sipe, the rubber itself is incompressible, so the groove width of the sipe formed in the block becomes narrow on the ice road surface with a low coefficient of friction. It turned out that the effect and water removal effect decreased, and ice performance fell. This phenomenon is likely to occur particularly when a sipe having a groove width of 0.6 mm or less is provided with a sipe density of 0.1 mm / mm ² or more.

  On the other hand, a studless tire having a block in which a large number of small holes are formed instead of a conventional sipe is known (for example, see Patent Document 1). By providing such a large number of small holes, it is possible to improve the ice performance without reducing the block rigidity, and to improve the wear resistance and the running performance on the dry road surface.

  However, when only a small hole is provided, the edge effect cannot be obtained, and the water removal effect is insufficient due to the small volume of the small hole, making it difficult to improve the braking performance and turning performance on the ice road surface. Met.

  Furthermore, a studless tire having a block in which a large number of recesses are formed in addition to a conventional sipe is known (see, for example, Patent Document 2). Such a large number of recesses are provided so that the edge effect can be exhibited even when the tire is new. Therefore, since the depth of the concave portion is shallow (0.75 mm in the embodiment), there was almost no effect of letting the deformation of the block under load load to the concave portion.

Japanese Patent Laid-Open No. 3-208705 JP-A-9-123713

  Accordingly, an object of the present invention is to provide a pneumatic tire capable of improving the ice braking performance and the ice turning performance by avoiding the narrowing of the sipe groove width when a load is applied.

The above object can be achieved by the present invention as described below.
That is, the pneumatic tire of the present invention is a pneumatic tire provided with a tread pattern having a land portion on which a sipe is formed. In the land portion, a sipe having a groove width of 0.2 to 0.6 mm has a sipe density of 0. In addition to being provided at 1 to 0.2 mm / mm ² , a plurality of small holes having a depth of 3 mm or more are provided along the sipe in the land portion divided by the sipe.

  According to the pneumatic tire of the present invention, the sipe groove width and the sipe density are in the above ranges, and therefore the sipe groove width is likely to be narrowed when a load is applied. Since a plurality of small holes having a depth are provided, the deformation of the rubber easily escapes to the small holes when a load is applied, so that the sipe groove width can be prevented from being narrowed. As a result, the sipe edge effect and water removal effect can be maintained, and the braking performance and turning performance on the ice road surface can be improved. In addition, the moderate deflection | deviation for improving ice performance comes to be obtained to a land part more suitably as it is in the range of said sipe density.

  In the above, the small hole preferably has a diameter of 0.5 to 2.0 mm. With such a small hole size, it is possible to sufficiently release the rubber deformation to the small hole when a load is applied, and to prevent the small hole from becoming too large and the rigidity of the land portion to be too low. Can do.

  Further, it is preferable that the land portion is formed as a block, and an area where the formation density of the small holes is relatively high or an area where the diameter of the small holes is relatively large is provided near the center of the block. The sipe groove width is likely to be narrower near the center than near the block because the deformation of the rubber under load is less likely to escape. According to this configuration, the deformation of the rubber near the center is effectively released. The ice performance can be improved more effectively.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a main part enlarged view showing an example of a land portion of a tread pattern in the pneumatic tire of the present invention.

  The pneumatic tire of the present invention includes a tread pattern having a land portion in which a sipe is formed. In the present embodiment, as shown in FIG. 1, an example in which a wavy sipe 10 is formed in the tire 1 in the tire width direction WD is shown. The portion other than the block 1 of the tread pattern may be any pattern. For example, a portion in which blocks are provided on the left and right of the block 1 may be mentioned. The block 1 is not limited to this shape, and may be any of a square, a parallelogram, a V-shape, a pentagon, a polygon, a curved block, or the like.

In the present invention, as shown in FIG. 1, a sipe 10 having a groove width of 0.2 to 0.6 mm is provided at a sipe density of 0.1 to 0.2 mm / mm ² in a block 1 that is a land portion. The present invention is particularly effective when the groove width of the sipe 10 is 0.2 to 0.5 mm and the sipe density is 0.12 to 0.18 mm / mm ² .

If the groove width of the sipe 10 is less than 0.2 mm, a sufficient edge effect or water removal effect cannot be obtained from the beginning, and if the groove width of the sipe 10 exceeds 0.6 mm, the problem caused by the narrowing of the groove is Although it is less likely to occur, step wear deteriorates. Moreover, if the sipe density is less than 0.1 mm / mm ² , sufficient edge effect and water removal effect cannot be obtained from the beginning. If the sipe density exceeds 0.2 mm / mm ² , the groove width is difficult to narrow. The rigidity of the land portion becomes too low and the land portion falls excessively, so the edge effect is reduced, and the ground contact area is reduced, resulting in a decrease in ice performance.

  The cross-sectional shape of the wavy sipe 10 is not limited to a shape close to a sine wave, and may be any shape such as a wavy line obtained by alternately combining straight lines and curves, or a shape close to a rectangular wave. Moreover, the sipe 10 may have a linear part where a cross-sectional shape becomes a straight line partially.

  In the present invention, the amplitude of the waved sipe 10 (the sum of the heights of the tops on both sides) is preferably 0.5 to 5 mm, more preferably 1 to 4 mm, in order to exhibit the characteristics of the waved sipe 10. Moreover, 1-6 mm is preferable and, as for the period (for example, distance between convex-convex peak parts) of the wave-shaped sipe 10, 1.5-4 mm is more preferable.

  Further, the groove depth of the wavy sipe 10 is preferably 30 to 80% of the main groove depth. The wavy sipe 10 is generally formed so as to be perpendicular to the block surface, but the sipe may be slightly inclined (for example, 15 ° or less) with respect to the normal line of the block surface.

  In the present invention, as shown in FIG. 1, the land portion 1 divided by the sipe 10 is provided with a plurality of small holes 11 having a depth of 3 mm or more along the sipe 10. The thickness is preferably 4 to 7 mm. If the depth of the small hole 11 is less than 3 mm, the effect of escaping the deformation of the block 1 under load is hardly obtained, and the ice performance cannot be improved.

  The small holes 11 may be provided in at least one of the land portions divided by the sipe 10, but the small holes 11 are preferably provided in the land portions on both sides divided by the sipe 10.

  The shape of the small hole 11 is not limited to a circle, and may be an ellipse, a rectangle, other polygons, or the like. The diameter of the small hole 11 (in the case of other than a circle, the diameter of a circle corresponding to the same area) is preferably 0.5 to 2.0 mm, and more preferably 1 to 1.5 mm. If the diameter is less than 0.5 mm, the effect of escaping deformation of the block 1 under load tends to be small, and if the diameter exceeds 2.0 mm, the ground contact area is greatly reduced, resulting in a decrease in ice performance. Tend to.

  The small hole 11 is preferably provided within a distance of 1 mm from the nearest sipe 10. The distance between the small holes 11 is preferably within 1.5 mm near the center of the block 1 where high formation density is required.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread pattern as described above, and any conventionally known material, shape, structure, manufacturing method, and the like can be employed in the present invention.

  Since the pneumatic tire of the present invention is provided with a tread pattern that can easily obtain an appropriate deflection for improving ice performance, and sufficiently maintain the edge effect and water removal effect, the ice performance can be improved. It is particularly useful as a studless tire (winter tire).

[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.

  (1) In the above-described embodiment, the example in which the wavy sipe is formed in the block is shown. However, the land portion in the present invention is a rib extending in the tire circumferential direction, a rib extending zigzag in the tire circumferential direction, or the like. May be. The shape of the sipe may be any of a straight sipe, a zigzag sipe, a three-dimensional sipe whose cross-sectional shape changes in the depth direction, and the like. Moreover, not only a double-sided open sipe but a single-sided open sipe and a closed sipe may be sufficient.

  (2) In the above-described embodiment, an example in which small holes having the same diameter are uniformly provided on the entire surface of the block has been shown. However, in the present invention, as shown in FIGS. The formation density of the holes may be changed, or the diameter of the small holes may be changed.

  The example shown in FIG. 2A is an example in which a region A1 in which the formation density of the small holes 11 is relatively high is provided near the center of the block 1. In the present invention, it is not necessary to provide the small holes 11 on the entire surface of the block 1, and the small holes 11 may be provided only near the center of the block 1, for example, as in the example shown in FIG. Also in this case, the region A1 in which the formation density of the small holes 11 is relatively high is provided near the center. In the example shown in FIG. 2B, two rows of small holes 11 are provided in the block piece 1a.

  The example shown in FIG. 3A is an example in which a region A2 in which the diameter of the small hole 11 is relatively large is provided near the center of the block 1. In the present invention, as shown in FIG. 3B, a region A <b> 3 in which the formation density of the small holes 11 is relatively high and the diameter of the small holes 11 is relatively large may be provided near the center of the block 1.

  (3) In the above-described embodiment, an example in which the center line (reference line) of the wavy sipe is formed in the tire width direction WD is shown. However, the center line of the wavy sipe is inclined with respect to the tire width direction WD. In that case, the inclination angle is preferably within 45 °.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Ice braking performance Tires are mounted on a real vehicle (domestic 3000cc class FR sedan), run on a frozen road under the load conditions of one passenger, and ABS is applied by applying braking force at a speed of 40km / h. The braking distance was evaluated with an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

(2) Ice turning performance The tires are mounted on the same actual vehicle as above, and the same road surface is run on the Remnis skate curve (8-shaped curve: R = 25m yen) under the load condition of one passenger, and the lap time is evaluated as an index. did. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

Comparative example 1 (conventional product)
Radial tires of size 205 / 65R15 were manufactured by forming sipes with the following sizes in a tread pattern having blocks (length 30 mm, width 30 mm) shown in FIG. Table 1 shows the results of each performance evaluation described above using this tire. The sipe depth was 5 mm, the groove width was 0.3 mm, the amplitude was 1.5 mm, and the sipe interval was 5 mm.

Example 1
In the tread pattern having the entire block shown in FIG. 1 (same as comparative example 1 except for sipes), small holes are formed in the following sizes (sipes are the same as in comparative example 1) and radials of size 205 / 65R15 Tires were manufactured. Table 1 shows the results of each performance evaluation described above using this tire. The small hole depth was 5 mm, the small hole diameter was 1.5 mm, and the small hole interval was 4 mm.

Example 2
In the tread pattern having the entire block shown in FIG. 2A (except for sipes, the same as in comparative example 1), small holes are formed in the following sizes (sipes are the same as in comparative example 1), and size 205 / A 65R15 radial tire was produced. Table 1 shows the results of each performance evaluation described above using this tire. The small hole depth was 5 mm, the small hole diameter was 1.5 mm, the small hole interval in the high density region was 4 mm, and the small hole interval in the low density region was 8 mm.

Example 3
In the tread pattern having the block shown in FIG. 3A on the entire surface (except for sipes, the same as in Comparative Example 1), small holes are formed in the following sizes (Sipe is the same as in Comparative Example 1), and size 205 / A 65R15 radial tire was produced. Table 1 shows the results of each performance evaluation described above using this tire. The small hole depth was 5 mm, the small hole interval was 4 mm, the small hole diameter was 2 mm, and the small hole diameter was 1.5 mm.

Comparative Example 2
In Example 1, a radial tire was manufactured in the same manner as in Example 1 except that the depth of the small holes was changed to 1 mm. Table 1 shows the results of each performance evaluation described above using this tire.

And if cut blocks of tires produced in Reference Test Example Comparative Example 1 at the same depth as the groove bottom of the circumferential groove which (block area 900 mm ^2), by contacting a tread on the glass surface, not a load, load 470kg The change in the groove width of the sipe was comparatively observed when the load was applied (corresponding to the load on the grounding portion when the vehicle was stopped). As a result, whereas in the former the total groove area of the sipe was 52.5 mm ^2, the total groove area of the sipe in the latter is 40 mm ^2, the total groove area is decreased 24% in the latter. On the other hand, in the block shown in FIG. 1 of Example 1, the total groove area of the sipe when a load was applied was 45 mm ² , and the amount of decrease in the groove area was small.

  As the result of Table 1 shows, in the Example, the ice braking performance and the ice turning performance were significantly improved as compared with the conventional products. In particular, in Examples 2 to 3 in which small holes were provided with a high density or a large diameter near the center of the block, the ice performance was further improved. On the other hand, in Comparative Example 2 in which the small holes were too shallow, it was not possible to avoid the narrowing of the sipe groove width when the load was applied, and the ice performance deteriorated.

The principal part enlarged view which shows an example of the land part in the pneumatic tire of this invention The principal part enlarged view which shows the other example of the land part in the pneumatic tire of this invention The principal part enlarged view which shows the other example of the land part in the pneumatic tire of this invention The principal part enlarged view which shows an example of the land part in the conventional pneumatic tire

Explanation of symbols

1 block (land)
10 Wavy sipe
11 Small hole WD Tire width direction

Claims (3)

In a pneumatic tire provided with a tread pattern having a land portion where a sipe is formed,
In the land portion, a sipe having a groove width of 0.2 to 0.6 mm is provided at a sipe density of 0.1 to 0.2 mm / mm ² , and the land portion divided by the sipe is along the sipe, A pneumatic tire having a plurality of small holes having a depth of 3 mm or more.   The pneumatic tire according to claim 1, wherein the small hole has a diameter of 0.5 to 2.0 mm.   The pneumatic structure according to claim 1, wherein the land portion is formed as a block, and a region where the formation density of the small holes is relatively high or a region where the diameter of the small holes is relatively large is provided near the center of the block. tire.

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